Medical history records asthma in the adolescent and in the adult is characterized by reversible airway obstruction, airway inflammation, and airway hyperactivity. Clinical manisfestations of asthma, such as wheezing and cough, are caused by airway obstruction, induced by reversible smooth-muscle constriction, edema and mucus secretion. Accepted medical evidence indicates asthma is an inflammatory disorder of the airways involving the production and activity of endogenous inflammatory mediators known as leukotrienes. The present treatment indicated for the management of this condition comprises the administration of a leukotriene-antagonist that produces a therapeutic benefit in the patient afflicted with asthma by inhibiting the action of leukotrienes at receptor sites on airway smooth muscles.
Leukotriene-antagonists are indicated by the medical and the pharmaceutical arts as anti-asthamatic agents for the treatment of asthma. The prior art treatment of asthma comprised administering orally a leukotriene-antagonist to a patient in need of repeated doses from once-to-four times a day. With this therapeutic profile, it is difficult to achieve continuous-prolonged therapy for the better management of asthma, as the program requires rigid compliance and it is cost ineffective.
The properties of the leukotriene-antagonists do not lend themselves to provide dosage form and drug formulations that can administer the leukotriene-antagonist at a controlled and known rate per unit time over an extended time to produce the intended therapy. For instance, the leukotriene-antagonists can be adversely affected by light, they can be insoluble in water, they can undergo a change in polymorphic form in the presence of water which results in decreased drug absorption, and they need protection from air. All of these are conditions that lead-away for sustained-release therapy in system.
It is self-evident from the above presentation a need exists for a delivery system selected from a dosage form and a drug formulation that can deliver the selected anti-asthmatic drug substantially protected from physical change and from the environment. The need exists to insure a complete dose of the anti-asthmatic drug is administered to a patient by the delivery system substantially independent of the changing environment of the gastrointestinal tract. Additionally, the need exists for a delivery system that can deliver a therapeutic dose of the selected anti-asthma drug for its intended effect and concurrently lessen the side-effects that can accompany the drug.
It will be appreciated by those in the dispensing art, that a need exists for a novel and unique sustained-release delivery system and for a method of administering an antiasthma drug in a rate-controlled dose over time. The need exists for a delivery system that can deliver a leukotriene-receptor antagonist from a sustained-release dosage form over twenty-four hours in a substantially constant dose per unit time for its beneficial therapeutic effect. Further, it will be acknowledged by those skilled in the dispensing art, that if such a novel and unique delivery system and method are made available that can administer the antiasthma drug in a sustained-release controlled dose over time, the delivery system and the method would represent an advancement and an unexpected contribution to the medical and pharmaceutical arts.